Thin film transistor and method for manufacturing the same

ABSTRACT

The present invention provides a thin-film transistor that is formed by using a patterning method capable of forming a semiconductor channel layer in sub-micron order and a method for manufacturing thereof that provides a thin-film transistor with a larger area, and suitable for mass production. These objects are achieved by a thin-film transistor formed on a substrate  1  with a finely processed concavoconvex surface  2 , in which a source electrode and a drain electrode are formed on adjacent convex portions of the concavoconvex surface  2 , with a channel and a gate being formed on a concave area between the convex portions. A gate electrode  5 , a gate insulating film  6  and a semiconductor channel layer  7  are laminated in this order on the concave area from the bottom surface of the concave portion toward the top surface. Preferably, in this thin-film transistor, the concavoconvex surface is formed of a curing resin, a semiconductor constituting a thin-film transistor is formed of a semiconductor such as polycrystal silicon or an organic semiconductor material, and the substrate is formed of glass, plastic or a composite material of these materials.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a field-effect type thin-filmtransistor in which a thin film semiconductor and an insulating materialare formed on a substrate with a concavoconvex surface, and a method formanufacturing the same.

2. Description of the Related Art

In general, upon manufacturing a thin-film transistor (TFT), an exposingdevice for transferring a necessary pattern onto a substrate is used.This exposing device is constituted by an exposing optical system fortransferring a fine pattern onto a substrate, an alignment system thatpositions a mask and the substrate with high precision, and an automatictransporting system that automatically transports the mask and thesubstrate. Prior to an exposing process in which such an exposing deviceis used, a resist thin film having predetermined photosensitivity isformed on the substrate.

In recent years, with respect to liquid crystal apparatuses, variousattempts are being made to achieve high performances of the liquidcrystal apparatus by providing high definition in the display accuracyand a low power-consumption driving process. As the performances of theliquid crystal apparatus become higher, the precision of TFT formed onthe liquid crystal display has been improved to a sub-micron level (<1μm), with the result that demands for fine patterning on wide area isincreasing.

In order to achieve such fine patterning, an exposing technique whichmeets the necessary degree of precision is required indispensably,however, an exposing device and an exposing technique with resolutionwhich completely satisfy such a degree of precision have not beencompleted from the viewpoint of throughputs, and superior techniquesneed to be developed.

Moreover, the integration of the DRAM that is a typical example of LSIin being improved in a remarkable degree, that is, four times in thesethree years. Accordingly, the miniaturization of the integrated circuitpattern is being improved, and there are practical needs for line-widthprocessing precision of not more than 130 nm.

Under these circumstances, as an example of a fine-patterning techniquegenerally used as a pattern-forming technique, a photolithographytechnique (for example, see “Flat Panel Display '91”, Setsuo USUI,published by Nikkei Business Publications, Inc., 1991, p. 117-128) canbe listed. As a fine-patterning technique for small quantity, largevariety products, a direct-drawing technique and the like using anelectron beam can be listed.

However, the above mentioned fine-patterning techniques have respectiveproblems. For example, in the photolithography technique, there is alimitation in the resolution in association with the light wavelength,and the problem that transferring and exposing in a scale of not morethan 100 nm are difficult has been pointed out (for example, see Journalof Japan Society of Grinding Engineers, by TANIGUCHI et al., publishedin 2002 vol. 46, issue 6, p.282-285). Moreover, in the direct drawingtechnique using an electron beam, it has been recognized that thethroughput per unit time is insufficient, and is not suitable for massproduction.

On the other hand, “Flat Panel Display '91”, Setsuo USUI, published byNikkei Business Publications, Inc., 1991, p. 117-128 introduces anano-imprint lithography technique as a fine-patterning techniquecapable of climbing out of the limitation of resolution in the abovementioned photolithography technique. This nano-imprint lithographytechnique is a technique in which: thermoplastic PMMA(polymethylmethacrylate) is provided to a pattern transferring layer ona silicon substrate, and a mold that has been preliminarily patterned ispressed onto the pattern transferring layer so that a fine concavoconvexpattern is formed on the PMMA resin layer. Thereafter, forming of awiring pattern by forming Al or the like is being studied. Moreover,Japanese Patent Application Laid-Open No. 11-204742 discloses atechnique in which a desired concavoconvex pattern is formed bytransferring concavoconvex of a stamp by using a 2P (Photo-Polymerized)method, which is a technique similar to the nano-imprint lithographytechnique.

However, the above mentioned nano-imprint lithography technique andtechniques similar thereto are still under development, and have notbeen fully researched, and in particular, with respect to thefield-effect type thin-film transistor and method for manufacturingthereof, there are no examples of the research and practicalapplication.

SUMMARY OF THE INVENTION

The present invention is achieved to solve the above mentioned problemswith the photolithography technique and direct drawing technique usingan electron beam, and its object is to provide a thin-film transistormanufactured by using a patterning method capable of formingsemiconductor channel layers in the sub-micron order, and a method formanufacturing thereof that provides a thin-film transistor with a largerarea, and suitable for mass production.

In order to achieve the above mentioned object, a first invention of athin-film transistor is a thin-film transistor formed on a substratewith a concavoconvex surface, on which: a source electrode and a drainelectrode are formed on adjacent convex portions of the concavoconvexsurface; and a semiconductor channel layer and a gate electrode areformed on a concave area between the convex portions.

The thin-film transistor of the first invention preferably includes thefollowing embodiments: (i) an embodiment in which, in the concave area,a gate electrode, a gate insulating film and a semiconductor channellayer are laminated in this order on the bottom surface of the concaveportion; and (ii) an embodiment in which, in the concave area, asemiconductor channel layer, a gate insulating film and a gate electrodeare laminated in this order on the bottom surface of the concaveportion.

Moreover in order to achieve the above mentioned object, a secondinvention of a thin-film transistor is a thin-film transistor formed ona substrate with a concavoconvex surface, on which: either one of asource electrode or a drain electrode is formed on a top surface of theconvex portion of the concavoconvex surface; a semiconductor channellayer and a gate electrode are formed on a side surface area connectingto the top surface of the convex portion; remaining one of the sourceelectrode or the drain electrode is formed on a bottom surface of aconcave portion connecting to the side surface area of the convexportion.

Further, in order to achieve the above mentioned object, a thirdinvention of a thin-film transistor is a thin-film transistor formed ona substrate with a concavoconvex surface, on which: a semiconductorchannel layer, a gate insulating film and a gate electrode are laminatedon the convex portion of the concavoconvex surface in this order; and asource electrode and a drain electrode are respectively formed on bottomsurfaces of both sides of the convex portion.

Here, the thin-film transistor of the first to third inventionspreferably includes the following modes: (1) a mode in which theconcavoconvex surface is formed of a curing resin, (2) a mode in whichthe semiconductor that forms the thin-film transistor is formed ofpolycrystal silicon or organic semiconductor material and (3) a mode inwhich the substrate is formed of a glass material, a plastic material ora composite material of these materials.

In order to achieve the above mentioned object, a first method formanufacturing a thin-film transistor of the invention is a method formanufacturing a thin-film transistor formed by forming a sourceelectrode and a drain electrode on adjacent convex portions of aconcavoconvex surface of a substrate with a concavoconvex surface, andlaminating a gate electrode, a gate insulating film and a semiconductorchannel layer in this order on a bottom surface of a concave areabetween the convex portions, comprising: (1) preparing a substrate and aconcavoconvex surface forming substrate on which a concavoconvex patternis formed; (2) after sandwiching a curing resin composition by the twosubstrates, curing the composition and demolding the concavoconvexsurface forming substrate to form a substrate with a concavoconvexsurface; (3) after forming a conductive thin film over the entiresurface of the concavoconvex surface, further forming a positive typeresist film thereon so that the concavoconvex surface is flattened; (4)exposing and developing the resist film by using a mask having the sameconcavoconvex pattern as the concavoconvex surface forming substrate, tobare the conductive thin film on the top surfaces of the convexportions; (5) forming an impurity containing amorphous silicon thin filmover the entire surface that has been bared; (6) removing the resistfilm and the impurity containing amorphous silicon thin film remainingin the concave areas by exposing and developing from the front side ofthe substrate; (7) etching the bared conductive thin film; (8) formingan amorphous silicon thin film over the entire surface of the substrateafter the etching; (9) carrying out a laser annealing process to form asemiconductor channel layer formed of polysilicon, as well ascrystallizing the impurity containing amorphous silicon thin film on thetop surfaces of the convex portion to form a source side diffusion layerand a drain side diffusion layer formed of low resistance polysilicon;(10) forming a gate insulating film on the semiconductor channel layer,the source side diffusion layer and the drain side diffusion layer; and(11) forming a gate electrode on the gate insulating film of the upperportion of the semiconductor channel layer.

In order to achieve the above mentioned object, a second method formanufacturing a thin-film transistor of the invention is a method formanufacturing a thin-film transistor formed by forming a sourceelectrode and a drain electrode on adjacent convex portion of aconcavoconvex surface of a substrate with a concavoconvex surface, andlaminating a semiconductor channel layer, a gate insulating film and agate electrode in this order on a bottom surface of a concave areabetween the convex portions, comprising: (1) preparing a substrate and aconcavoconvex surface forming substrate on which a concavoconvex patternis formed; (2) after sandwiching a curing resin composition by the twosubstrates, curing the composition and demolding the concavoconvexsurface forming substrate to form a substrate with a concavoconvexsurface; (3) after forming an impurity containing amorphous silicon thinfilm over the entire surface of the concavoconvex surface, furtherforming a negative type resist film thereon so that the concavoconvexsurface is flattened; (4) exposing and developing the resist film byusing a mask having the same concavoconvex pattern as the concavoconvexsurface forming substrate, to bare the impurity containing amorphoussilicon thin film on the concave area; (5) etching the bared impuritycontaining amorphous silicon thin film; (6) removing the resist filmremaining on the top surfaces of the convex portions; (7) forming anamorphous silicon thin film on a predetermined area; (8) carrying out alaser annealing process to form a semiconductor channel layer formed ofpolysilicon on the concave area, as well as crystallizing the impuritycontaining amorphous silicon thin film on the top surfaces of the convexportions on both sides of the concave portion to form a source sidediffusion layer and a drain side diffusion layer formed of lowresistance polysilicon; (9) forming a gate insulating film over theentire surface; and (10) after forming a contact hole in the gateinsulating film, forming a conductive thin film to form a sourceelectrode, a gate electrode and a drain electrode.

In order to achieve the above mentioned object, a third method formanufacturing a thin-film transistor of the invention is a method formanufacturing a thin-film transistor formed by forming either one of asource electrode or a drain electrode on a top surface of a convexportions of a concavoconvex surface of a substrate with a concavoconvexsurface, forming a semiconductor channel layer and a gate electrode on aside surface area connecting to the top surface of the convex portion,forming the remaining one of the source electrode or the drain electrodeon a bottom surface of a concave portion connecting to the side surfacearea of the convex portion, comprising: (1) preparing a substrate and aconcavoconvex surface forming substrate on which a concavoconvex patternis formed; (2) after sandwiching a curing resin composition by the twosubstrates, curing the composition and demolding the concavoconvexsurface forming substrate to form a substrate with a concavoconvexsurface; (3) after forming a conductive thin film over the entiresurface of the concavoconvex surface, further forming an impuritycontaining amorphous silicon thin film thereon, and further forming apositive type resist film thereon so that the concavoconvex surface isflattened; (4) after positioning a photomask, having an opening portionwhich is a size similar to the film thickness of the conductive thinfilm and the impurity containing amorphous silicon thin film that areformed on the side surface area of a step portion of the concavoconvexsurface, on the side surface area on the positive type photoresist filmto be made in contact therewith, exposing and developing from thephotomask side to remove the resist film on the side surface area; (5)etching to remove the bared impurity containing amorphous silicon thinfilm and the conductive thin film; (6) removing the resist film on theconcavoconvex surface; (7) forming an amorphous silicon thin film on apredetermined area including the side surface area; (8) carrying out alaser annealing process to form a semiconductor channel layer formed ofpolysilicon on the side surface area, as well as crystallizing theimpurity containing amorphous silicon thin film of the top surfaces ofthe convex portions and bottom surface of the concave portion connectingto the side surface area to form a source side diffusion layer and adrain side diffusion layer formed of low resistance polysilicon; (9)forming a gate insulating film on the crystallized polysilicon; and (10)forming a gate electrode on the gate insulating film.

In order to achieve the above mentioned object, a fourth method formanufacturing a thin-film transistor of the invention is a method formanufacturing a thin-film transistor formed by laminating asemiconductor channel layer, a gate insulating film and a gate electrodein this order on a convex portions of a concavoconvex surface of asubstrate with a concavoconvex surface, and forming a source electrodeand a drain electrode respectively on a bottom surface of both sides ofthe concave area between the convex portions, comprising: (1) preparinga substrate and a concavoconvex surface forming substrate on which aconcavoconvex pattern is formed; (2) after sandwiching a curing resincomposition by the two substrates, curing the composition and demoldingthe concavoconvex surface forming substrate to form a substrate with aconcavoconvex surface; (3) after laminating a conductive thin film andan impurity containing amorphous silicon thin film over the entiresurface of the concavoconvex surface, further forming a positive typeresist film so that the concavoconvex surface is flattened; (4) exposingand developing the resist film by using a mask having the sameconcavoconvex pattern as the concavoconvex surface forming substrate, tobare the impurity containing amorphous silicon thin film on the topsurfaces of the convex portions; (5) removing the impurity containingamorphous silicon thin film and the conductive thin film bared by anetching; (6) removing the resist film on the concavoconvex surface; (7)forming an amorphous silicon thin film on a predetermined area includingthe top surfaces of the convex portions; (8) carrying out a laserannealing process to form a semiconductor channel layer formed ofpolysilicon on the top surfaces of the convex portions, as well ascrystallizing the impurity containing amorphous silicon thin film formedon concave areas on both sides of the top surface of the convex portionto form a source side diffusion layer and a drain side diffusion layerformed of low resistance polysilicon; (9) forming a gate insulating filmon the crystallized polysilicon; and (10) forming a gate electrode onthe gate insulating film.

In order to achieve the above mentioned object, a fifth method formanufacturing a thin-film transistor of the invention is a method formanufacturing for a thin-film transistor formed by laminating asemiconductor channel layer, a gate insulating film and a gate electrodein this order on a convex portion of a concavoconvex surface of asubstrate with a concavoconvex surface, and forming a source electrodeand a drain electrode formed respectively on bottom surface on bothsides of the convex portion, comprising: (1) preparing a substrate and aconcavoconvex surface forming substrate on which a concavoconvex patternis formed; (2) after sandwiching a curing resin composition by the twosubstrates, curing the composition and demolding the concavoconvexsurface forming substrate to form a substrate with a concavoconvexsurface; (3) after laminating a conductive thin film over the entiresurface of the concavoconvex surface, further forming a negative typeresist film thereon so that the concavoconvex surface is flattened; (4)exposing and developing the resist film by using a mask having the sameconcavoconvex pattern as the concavoconvex surface forming substrate, tobare the conductive thin film on the concave portion; (5) removing theconductive thin film bared by an etching; (6) removing the resist filmon the concavoconvex surface; (7) forming a gate insulating film overthe entire surface thereof; (8) forming an amorphous silicon thin filmon the gate insulating film, and further forming an impurity containingamorphous silicon thin film on the amorphous silicon thin film; (9)carrying out a laser annealing process to form a semiconductor channellayer formed of polysilicon on the top surfaces of the convex portions,as well as crystallizing the impurity containing amorphous silicon thinfilm formed on concave areas on both sides of the top surface of theconvex portion to form a source side diffusion layer and a drain sidediffusion layer formed of low resistance polysilicon; and (10) forming asource electrode on the source side diffusion layer, and forming a drainelectrode on the drain side diffusion layer.

Different from a conventional TFT manufacturing method using agenerally-used photolithography technique, by the methods formanufacturing according to the first to fifth inventions, since aconcavoconvex surface formed of a curing resin is formed on a substrateby using a concavoconvex surface forming substrate to the substrate, andthe concave portion of the concavoconvex surface is used as a TFTsemiconductor channel layer, it is possible to equalize and refine thesemiconductor channel layer by improving the degree of precision of theconcavoconvex surface using the concavoconvex surface forming substrate.Consequently, it becomes possible to easily manufacture a thin-filmtransistor having a semiconductor channel layer in the sub-micron order,and also to provide a method for manufacturing that achieves a thin-filmtransistor with a larger area, and suitable for mass production.

As described above, according to the thin-film transistor of the presentinvention, since the concavoconvex surface is formed with minutestructure, it is possible to provide extremely fine thin-film transistorutilizing the concavoconvex shape. Moreover, since the elementsconstituting the thin-film transistor of the present invention can bevaried within the range of the fine shape of the concavoconvex surface,it is possible to provide extremely fine thin-film transistor.

According to the method for manufacturing the thin-film transistor ofthe present invention, different from a conventional TFT manufacturingmethod using a generally-used photolithography technique, since aconcavoconvex surface formed of a curing resin is formed on a substrateby using a concavoconvex surface forming substrate to the substrate, andthe concave portion of the concavoconvex surface is used as a TFTsemiconductor channel layer, it is possible to equalize and refine thesemiconductor channel layer, by improving the degree of precision of theconcavoconvex surface using the concavoconvex surface forming substrate.Consequently, it becomes possible to easily manufacture a thin-filmtransistor having a semiconductor channel layer in the sub-micron order,and also to provide a method for manufacturing that achieves a thin-filmtransistor with a larger area, and suitable for mass production.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view that shows one example of a thin-filmtransistor of a first embodiment of the present invention.

FIG. 2 is a cross-sectional view that shows one example of a thin-filmtransistor of a second embodiment of the present invention.

FIG. 3 is a cross-sectional view that shows one example of a thin-filmtransistor of a third embodiment of the present invention.

FIG. 4 is a cross-sectional view that shows one example of a thin-filmtransistor of a fourth embodiment of the present invention.

FIG. 5 is a cross-sectional view that shows one example of a thin-filmtransistor of a fifth embodiment of the present invention.

FIGS. 6A to 6L are process drawings that show a first example of amethod for manufacturing a thin-film transistor of the presentinvention.

FIGS. 7A to 7K are process drawings that show a second example of amethod for manufacturing the thin-film transistor of the presentinvention.

FIGS. 8A to 8J are process drawings that show a third example of amethod for manufacturing the thin-film transistor of the presentinvention.

FIGS. 9A to 9J are process drawings that show a fourth example of amethod for manufacturing the thin-film transistor of the presentinvention.

FIGS. 10A to 10K are process drawings that show a fifth example of amethod for manufacturing the thin-film transistor of the presentinvention.

FIGS. 11A and 11B are a photomicrograph of a surface of a concavoconvexsurface forming substrate used for forming a concavoconvex surface and aphotomicrograph of the concavoconvex surface formed on a substrate thatis applied to a thin-film transistor of the present invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

The thin-film transistor and the method for manufacturing the same ofthe present invention will be described below referring to the drawings.FIG. 1 is a cross-sectional view that shows one example of a thin-filmtransistor of the first embodiment of the present invention, FIG. 2 is across-sectional view that shows one example of a thin-film transistor ofthe second embodiment of the present invention, FIG. 3 is across-sectional view that shows one example of a thin-film transistor ofthe third embodiment of the present invention, FIG. 4 is across-sectional view that shows one example of a thin-film transistor ofthe fourth embodiment of the present invention, and FIG. 5 is across-sectional view that shows one example of a thin-film transistor ofthe fifth embodiment of the present invention. Moreover, FIGS. 6 to 10are explanatory drawings that show each process of the method formanufacturing the thin-film transistor of the present invention.

(Thin-film Transistor)

The thin-film transistor of the present invention is characterized inthat it is formed on a substrate with a concavoconvex surface.

As shown in FIGS. 1 and 2, in thin-film transistors of the first andsecond embodiments, a source (hereinafter, when simply referred to as“source”, this indicates a structure including a source electrode 3 anda source side diffusion layer 8) and a drain (hereinafter, when simplyreferred to as “drain”, this indicates a structure including a drainelectrode 4 and a drain side diffusion layer 9) are formed on adjacentconvex portions of the concavoconvex surface, and a semiconductorchannel layer 7 and a gate (hereinafter, when simply referred to as“gate”, this indicates a structure including a gate electrode 5 and agate insulating film 6) are formed on a concave area between the convexportions.

Among these, in the concave area of the thin-film transistor of thefirst embodiment, as shown in FIG. 1, a gate electrode 5, a gateinsulating film 6 and a semiconductor channel layer 7 are laminated, inthis order from the bottom toward the top, on the bottom surface of theconcave portion. Moreover, on the top surface of one of the adjacentconvex portions located on both sides of the concave area, a sourceelectrode 3 and a polycrystal silicon layer which is a source sidediffusion layer 8 are laminated in this order, and on the top surface ofthe other convex portion, a drain electrode 4 and a polycrystal siliconlayer 9 which is a drain side diffusion layer 9 are laminated in thisorder.

Moreover, in the concave area of the thin-film transistor of the secondembodiment, as shown in FIG. 2, a semiconductor channel layer 7, a gateinsulating film 6 and a gate electrode 5 are laminated, in this orderfrom the bottom toward the top, on the bottom surface of the concaveportion. Moreover, on the top surface of one of the adjacent convexportions located on both sides of the convex area, a polycrystal siliconlayer which is a source side diffusion layer 8 and a source electrode 3are laminated in this order via a contact hole 10 formed in the gateinsulating film 6, and on the other top surface of the other convexportion, a polycrystal silicon layer which is a drain side diffusionlayer 9.and a drain electrode 4 are laminated in this order via thecontact hole 10 formed in the gate insulating film 6.

In the thin-film transistor of the third embodiment, as shown in FIG. 3,either one of the source electrode 3.or the drain electrode 4 is formedon the top surface of a convex portion of the concavoconvex surface 2,and a semiconductor channel layer 7 and a gate electrode 5 are formed ona side surface area connecting to the top surface of the convex portion,and the remaining one of the source electrode 3 or the drain electrode 4is formed on a bottom surface of the concave portion connecting to theside surface of the convex portion. For more detailed explanationreferring to an example shown in FIG. 3, on the top surface of theconvex portion, the source electrode 3, the polycrystal silicon layerwhich is the source side diffusion layer 8 and the polycrystal siliconlayer which is the semiconductor channel layer 7 are laminated in thisorder, and on the bottom surface of the concave portion, the drainelectrode 4, the polycrystal silicon layer which is the drain sidediffusion layer 9 are laminated in this order. The polycrystal siliconlayer which is the semiconductor channel layer 7 is provided so as tocover the source side diffusion layer 8 on the top surface of the convexportion from the side surface of the convex portion, and the gateinsulating film 6 is provided so as to cover the semiconductor channellayer 7 and the drain side diffusion layer 9 on the bottom surface ofthe concave portion. Moreover, the gate electrode 5 is provided on thegate insulating film 6 on the side surface of the convex portion.

As shown in FIG. 4, in the thin-film transistor of the fourthembodiment, the semiconductor channel layer 7, the gate insulating film6 and the gate electrode 5 are laminated in this order on the topsurface of the convex portion of the concavoconvex surface 2 insuccession, and the source electrode 3/source side diffusion layer 8 andthe drain electrode 4/drain side diffusion layer 9 are respectivelyformed on each bottom surfaces located on both sides of the convexportion.

As shown in FIG. .5, in the thin-film transistor of the fifthembodiment, the gate electrode 5, the gate insulating film 6 and thesemiconductor channel layer 7 are laminated in this order on the topsurface of the convex portion of the concavoconvex surface 2, and thesource side diffusion layer 8/source electrode 3 and the drain sidediffusion layer 9/drain electrode 4 are respectively formed on eachbottom surfaces located on both sides of the convex portion.

Since the thin-film transistor of the present invention having the abovementioned features is formed on the fine concavoconvex surface withsuperior dimensional precision, the source, the drain, the gate and thesemiconductor channel layer are formed in the fine scale. Consequently,in this thin-film transistor, the channel portion to be formed can beformed uniformly over a large area, making it possible to form athin-film transistor having uniform performances into a large area.Moreover, it becomes possible to achieve semiconductor channel layers inthe sub-micron order (for example, in the order of not more than 100 nm)that have been recently required.

The following description will discuss the respective components:

The substrate 1 constitutes a circuit substrate of the thin-filmtransistor, and examples of the material thereof include: inorganicmaterials such as glass, silicon wafers and quartz, or organicmaterials, such as polyamide, polyacetal, polybutylene terephthalate,polyethylene terephthalate, polyethylene naphthalate, orsyndio-tactics-polystyrene; polyphenylene sulfide, polyether etherketone, liquid crystal polymers, fluororesin, or polyether nitrile;polycarbonate, modified polyphenylene ether, polycyclohexene, orpolynorbornane-based resins; or polysulfone, polyether sulfone,polyallylate, polyamideimide, polyether imide or thermoplasticpolyimide, or composite materials of these. Moreover, with respect tothe organic materials, those formed of usual plastics may also be used.In particular, in the case when the substrate 1 is formed of an organicbase material, the thickness thereof is preferably set in a range of 5μm to 1000 μm, and more preferably, those materials having a thin,flexible film shape with a thickness in a range of 5 μm to 300 μm areused; thus, the substrate on which the thin-film transistor is formedcan be flexible.

The concavoconvex surface is formed on the substrate 1 with a curingresin. With respect to the curing resin composition to be used to formthe concavoconvex surface, examples thereof include: curing resins, suchas unsaturated polyesters, melamine, epoxy, polyester (metha)acrylate,urethane (metha)acrylate, epoxy (metha)acrylate, polyether(metha)acrylate, polyol (metha)acrylate, melamine (metha)acrylate ortriazine-based acrylate; and each of these may be used alone, or two ormore kinds of these may be used in a mixed state. If necessary, a curingagent, a photopolymerization initiator or the like may be added to thecuring resin composition, and can be used as curing resin such as athermosetting resin composition or an ionizing radiation curing resincomposition such as an ultraviolet curing resin composition. The curingresin composition preferably has a viscosity that is suitable forcoating, and a solvent or a monomer may be added so as to adjust theviscosity. As will be described later, the above mentioned curing resincomposition is cured by heat, ultraviolet rays, ionizing radiation orthe like, in a sandwiched state between the substrate land theconcavoconvex surface forming substrate, so as to have a desired fineshape.

The present invention is characterized in that the concavoconvex surfaceis formed over a large area with high precision, and formation of aminute structure in the sub-micron order is possible. By utilizing theconcavoconvex shape, it becomes possible to provide a thin-filmtransistor with extreme uniformity, as well as a very fine thin-filmtransistor. Consequently, as to the scale of the concavoconvex surface,the width of the bottom surface of the concave portion is preferably setin a range of 10 nm to 100,000 nm, the height from the bottom surface ofthe concave portion to the top surface of the convex portion ispreferably set in a range of 50 nm to 10, 000 nm, and the width of thetop surface of the convex portion is preferably set in a range of 10 nmto 100,000 nm. Because the thin-film transistor of the present inventionis formed on the concavoconvex surface that may be varied desirablywithin these ranges, it is possible to provide extremely fine element.Here, FIG. 11B is a photomicrography that shows a concavoconvex surfaceprovided on a substrate adopted to a thin-film transistor of the presentinvention, and FIG. 11A is a photomicrography that shows a surface of aconcavoconvex surface forming substrate to be used for forming theconcavoconvex surface.

The present method makes it possible to form extremely fine structure,and its structure preparation tests show that a structure of 0.1 μm/0.3μm can beformed (see the photograph). Moreover, it has been found that astructure of 10 nm can also be formed, which indicates the possibilityof a patterning exceeding the photolithography.

With respect to the respective elements constituting the thin-filmtransistor, those materials generally used conventionally may beadopted. For example, with respect to the source electrode 3, drainelectrode 4 and gate electrode 5, electrode materials including Al, Cuand the like may be preferably used, and the thickness is set in a rangeof 10 nm to 1000 nm. Moreover, the polycrystal silicon film constitutingthe source side diffusion layer 8 and the polycrystal silicon filmconstituting the drain side diffusion layer 9 are formed of lowresistance polycrystal silicon doped with impurities, in the same manneras the conventional material. Moreover, the semiconductor channel layer7 is formed of generally used polycrystal silicon. Here, the polycrystalsilicon films that constitute each diffusion layer can be obtained bycrystallizing an amorphous silicon film preliminarily formed, by a laserannealing process and the like, as will be described later in the methodfor manufacturing.

Here, the semiconductor channel layer 7 may be formed by a semiconductorother than the polycrystal silicon film, those materials that have beenwidely used as semiconductor materials for use in thin-film transistorsor those being examined as semiconductor materials may be adopted, andwith respect to the other inorganic compound semiconductor materials,hydrogenated amorphous silicon, hydrogenated amorphous silicongermanium, hydrogenated amorphous silicon carbide, crystallite silicon,polycrystal silicon and the like can be used. Moreover, materials suchas CdS, ZnS, or a mixed crystal of CdS and ZnS, CdTe or Se may be used.

With respect to the organic semiconductor materials, preferable examplesthereof include: π-electron conjugate type aromatic compounds, chaincompounds, organic pigments and organic silicon compounds. Specificexamples thereof include: pentacene, tetracene, thiophene oligomerderivatives, phenylene derivatives, phthalocyanine compounds,polyacetylene derivatives, polythiophene derivatives and cyaninepigments, however, materials are not limited to the above.

Moreover, a protecting film, a light shielding layer, a complementarythin-film transistor and the like may be formed further on the thin-filmtransistor. With respect to the protecting film, a SiO₂ film, a SiN filmor the like may be formed by a sputtering method or the like.

(Method for Manufacturing Thin-film Transistor)

The above mentioned thin-film transistor having a minute structure canbe manufactured by the following method. The example for the method formanufacturing shown here relates to the first embodiment that will bedescribed later, and specific descriptions thereof can be applied to anyof the methods for manufacturing relating to the second to fourthembodiments that will be described later.

(1) First, as shown in FIG. 6A, a substrate 1 to be used for forming athin-film transistor and a concavoconvex surface forming substrate 21,on which a concavoconvex surface forming pattern 22 (hereinafter,referred to as pattern 22) is formed, are prepared. Here, the samesubstrate 1 as described above is used.

With respect to the elements forming the concavoconvex surface formingsubstrate 21, the same materials as those forming the substrate 1 maybeused. In the case where the concavoconvex surface forming substrate 21is also used as a mask 25 which will be described later, it ispreferably be formed of a material that has transparency for exposinglight such as UV rays. The thickness of the concavoconvex surfaceforming substrate 21 may be desirably set, and from the viewpoint ofdimensional stability, a thick one is preferable. When glass or quartzis used as the base material, the thickness is normally set in a rangeof 1 mm to 5 mm, and in the case of an organic base material, thethickness is normally set in a range of 50 μm to 1000 μm.

The pattern 22, formed on the concavoconvex surface forming substrate,is prepared by forming a material such as a photocuring resin layer,that can be patterned, on the substrate 21 and then patterning thematerial. With respect to the pattern 22, either a thin film layer of aninorganic substance such as chromium, or a layer of a resin compositioncontaining a dye, a pigment or the like, may be used. When the pattern22 is constituted by the presence and absence of a layer of an inorganicsubstance such as chromium, the pattern 22 may be formed by using aphoto-etching method in the same manner as the photo-mask method formanufacturing for a semiconductor. Alternatively, the pattern 22 may beformed by a method in which a photosensitive resin layer, formed on abase material by coating or laminating, is subjected to pattern exposingand developing.

The pattern 22 is constituted by concave-shaped portions that formconvex portions on the substrate and convex-shaped portions that formconcave portions on the substrate, which will be described later. Here,since the concavoconvex surface forming substrate 21 also serves as astamper that gives the shape of the concavoconvex surface 21 on thesubstrate 1 forming a thin-film transistor, the thickness of the pattern22 is formed with high precision, for example, within a range of 50 nmto 10,000 nm. Moreover, the width of the pattern 22 and the widthdimension of the pattern intervals are formed with high precision withina range of 10 nm to 100,000 nm. The cross sectional shape of the pattern22 is preferably formed into a shape close to a square as possible, andin a case where corners of the cross sectional shape is rounded, thecurvature radius “r” thereof is preferably not more than 1/10 of thethickness of a light-shielding layer.

In the method for manufacturing of the present invention, a substratehaving the same pattern shape as the concavoconvex surface formingsubstrate 21 may be used later as an exposing mask 25. When the same oneis used as the concavoconvex surface forming substrate 21 and theexposing mask 25, the pattern is preferably formed to have lightshielding property. With respect to the method for forming the lightshielding pattern, the same methods as those conventionally used may beadopted, and for example, the pattern 22 may be formed of a chromiumthin film or the like, or the pattern 22 may be formed of a compositioncontaining a light-shielding dye or a pigment.

(2) Next, as shown in FIG. 6A, after sandwiching a curing resincomposition by the two substrates 1 and 21, the curing resin compositionis cured, and then, the concavoconvex surface forming substrate 21 isdemolded so that a substrate with a concavoconvex surface 2, formed ofthe curing resin, is formed.

In other words, the substrate 1 and the concavoconvex surface formingsubstrate 21 are superimposed so that the pattern 22 is on the substrate1 side and with the curing resin composition being sandwiched inbetween. The material to be sandwiched in between the two substrates isnot necessarily limited to the curing resin composition, however,considering the heat applied upon forming various thin-films in thesucceeding processes and the application of the thin-film transistor, itis preferable to use a curing resin composition with properties such ashigh heat resistance and high durability.

At this time, the resin composition may be sandwiched in between thesubstrate 1 and the concavoconvex surface forming substrate 21 by:coating either one or the both of the surface of the substrate 1 and thepattern surface of the concavoconvex surface forming substrate 2.1 witha curing resin composition, and then superimposing the above twosubstrates; or fixing the two substrates With a clearance in betweeneach other, and injecting the curing resin composition in between.

The curing of the curing resin composition is carried out by letting thecomposition stand for a predetermined period of time at normaltemperature or in a heated state. Moreover, in the case where anionizing radiation curing resin composition such as an ultravioletcuring resin composition is used, the curing can be carried out byirradiating the curing resin composition with ionizing radiation such asUV rays (Ultraviolet rays). Here, when curing by irradiating ionizingradiation, the irradiation is preferably carried out from the side ofthe one having an ionizing radiation transmitting property among thesubstrate 1 and the concavoconvex surface forming substrate 21.

Thereafter, by demolding the concavoconvex surface forming substrate 21,a concavoconvex surface 2 having a minute concavoconvex pattern formedof the curing resin is formed on the substrate 1. The thickness, theheight, the width and the like of the concavoconvex surface aredetermined as described above.

(3) Next, as shown in FIG. 6B, after forming a conductive thin film 23over the entire surface of the concavoconvex surface 2, a resist film 24is further formed thereon so that the concavoconvex surface 2 isflattened. The conductive thin film 23 is eventually formed into sourceelectrodes 33, drain electrodes 34 and gate electrodes 35, and for thisreason, Al, Cu and other electrode materials are preferably used as thethin film material, and is formed into a film by a known thin-filmforming method such as sputtering. The thickness of the conductive thinfilm 23 is normally in a range of 10 nm to 1000 nm.

For example, a positive type photoresist and the like are preferablyused as the resist film 24. The resist film is formed with the positivetype photoresist because the resist on the convex portions can bedissolved and removed with a mask that will be described later. Theresist film 24 is preferably formed by coating resist over the entiresurface using a spinner or the like and cured so that the concavoconvexsurface 2 is flattened. The reason that the resist film 24 is formed sothat the concavoconvex surface 2 is flattened is because a mask, whichwill be described later, can be closely contacted to the resist film 24;thus, it becomes possible to prevent light scattering caused by theconcavoconvex, and to improve the uniformity of the pattern.

(4) Next, as shown in FIGS. 6C and 6D, a mask 25 with the sameconcavoconvex pattern 26 as the concavoconvex surface forming substrate21, is used to expose and develop the resist film 24 so that theconductive thin film 23 on the top surface of the convex portion isbared.

A mask prepared by forming a light shielding pattern, formed of a lightshielding material such as chromium, on a glass substrate may be used asthe mask 25. With respect to the method for forming the light shieldingpattern, the same processes as those conventionally used may be adopted.For example, the pattern 22 may be formed with a chromium thin film orthe like, or the pattern 22 may be formed with a composition containinga light shielding dye or pigment. Here, the mask 25 is preferably usedalso as the above mentioned concavoconvex surface forming substrate 21.

(5) Next, as shown in FIG. 6E, an impurity containing amorphous siliconthin film 29 is formed over the entire surface which is bared. Theimpurity is contained because, in the later performed laser annealingprocess, a low resistance polycrystal silicon thin film can be formed,also in order to get ohmic contact to the metal electrodes. The dopingof impurities into the amorphous silicon is carried out by sputtering orthe like using a silicon target doped with the impurities. With respectto the method for forming the thin film 29, a vapor deposition method, aCVD method and the like can be listed in addition to the sputteringmethod. The thickness of the impurity containing amorphous silicon thinfilm is normally in a range of 5 nm to 50 nm.

(6) As shown in FIGS. 6F and 6G, exposing and developing processes arecarried out from the front surface of the substrate 1 so that the resistfilm 24 and the impurity containing amorphous silicon thin film 29remaining in the concave area are removed. By irradiating exposing lightfrom the front surface of the substrate, the positive type photoresistformed in the concave area is made to be dissolvable. The dissolvableresist film is dissolved in a developing solution so that the resistfilm 24 and the impurity containing amorphous silicon thin film 29 onthe concave area are removed.

(7) Next, as shown in FIG. 6H, the conductive thin film 23 on the baredportion is etched. With respect to the etching solution, a generallyused etching solution, such as a mixed solution of nitric acid andphosphoric acid and the like may be used. The impurity containingamorphous silicon thin film 29 acts as a resist film, and the substrateafter etching is provided with a conductive thin film 23 and an impuritycontaining amorphous silicon thin film 29 on the top surface of theconvex portion.

(8) Next, as shown in FIG. 6I, an amorphous silicon thin film 31 isformed over the entire surface of the substrate that has been subjectedto the etching process. The amorphous silicon thin film 31 is formed bya sputtering method using a silicon target containing no impurities, avapor deposition method, a CVD method or the like. The thickness of theamorphous silicon thin film 31 is normally set in a range of 30 nm to300 nm.

(9) As shown in FIGS. 6J and 6K, at the same time of forming asemiconductor channel layer 37 formed of polysilicon by a laserannealing process, a source side diffusion layer 38 and a drain sidediffusion layer 39, formed of low resistance polysilicon, are formed bycrystallizing the impurity containing amorphous silicon thin film on thetop surface of the convex portion. The laser annealing process is acrystallizing method in which the amorphous silicon thin film iscrystallized to form polysilicon (polycrystal silicon), and may becarried out by using various laser devices such as a XeCl excimer laserand a CW (Continuous Wave) laser. Here, after the crystallization, inorder to eliminate defects of silicones on the polycrystal gainboundaries, a hydrogen plasma treatment and a H₂O vapor treatment arealso effectively used. Moreover, in the case where no impuritycontaining amorphous silicon thin film is formed, an ion doping may becarried out before or after the laser annealing process to form thesource side diffusion layer 38 and the drain side diffusion layer 39.

(10) Next, as shown in FIG. 6(I), a gate insulating film 36 is formed onthe semiconductor channel layer 37, the source side diffusion layer 38and the drain side diffusion layer 39. With respect to the gateinsulating film 36, a SiO₂ thin film is preferably used, and, forexample, a film forming method such as reactive sputtering may be used.Moreover, other film forming methods (CVD method by TEOS, organic thinfilm, and the like) may be used.

(11) Next, a gate electrode 35 is formed on the gate insulating film 36on the upper portion of the semiconductor channel layer. The gateelectrode 35 can be formed by a film forming process such as sputteringby using the same conductive material, such as Al, Cu and the like, asthe above mentioned source electrode 3 and the drain electrode 4.

According to the first method for manufacturing as mentioned above,unlike the conventional TFT manufacturing method using the generalphotolithography technique, a concavoconvex surface formed of a curingresin is formed on the substrate by using a concavoconvex surfaceforming substrate, and the concave portion of the concavoconvex surfaceis used as a semiconductor channel layer of the TFT; thus, by improvingthe degree of precision of the concavoconvex surface using the abovementioned concavoconvex surface forming substrate, the semiconductorchannel layer can be uniformed and miniaturized. Consequently, itbecomes possible to easily manufacture a thin-film transistor having asemiconductor channel layer in the order of not more than 100 nm, andalso to provide a method for manufacturing that achieves a thin-filmtransistor with a larger area, and suitable for mass production.

First Embodiment

After formed a Cr thin film layer having a thickness of 500 nm on aquartz substrate, a predetermined pattern 22 was formed by aphoto-etching method so that a concavoconvex surface forming substrate21 was manufactured (FIG. 6A). At this time, the pattern 22 had anarrangement in which concave portions, each having a depth of 500 nmwith a width of 10 μm, were aligned face to face with a gap between twoconcave portions of 10 μm.

Between the pattern 22 of this concavoconvex surface forming substrate21 and a substrate 1 formed of non-alkali glass (1737, manufactured byCorning, Inc) having a thickness of 0.7 mm, an uncured transparent UVcuring resin composition was sandwiched and laminated, and this wasexposed to UV-rays from the substrate 1 side so that the UV curing resincomposition was cured. Thereafter, a concavoconvex surface 2 havingconvex portions having a line width of 10 μm and a height of 500 nm,with a gap between two convex portions of 10 μm, was formed on thesubstrate 1 by demolding the concavoconvex surface forming substrate 21(FIG. 6A).

After forming an Al thin film 23.having a thickness of 500 nm over theentire surface of the resulting concavoconvex surface 2 by sputteringmethod, a positive type photoresist (trade name: PMER P-LA900,manufactured by Tokyo Ohka Kogyo Co., Ltd.) was coated thereto by aspinner, and after. coating, this was heated at 80° C. for 30 minutes toform a positive type photoresist film 24 having a thickness of 8 μm. Atthis time, the surface of the resist film 24 was flattened (FIG. 6B).

The previously used concavoconvex surface forming substrate 21 wasaligned on the positive type photoresist film 24 at the same position asthe concavoconvex surface 2 was formed, and made closely contactedtherewith so that the side of the pattern 22 was made in contact withthe positive type photoresist film 24, and this was exposed toultraviolet rays 27 from the concavoconvex surface forming substrate 21side (FIG. 6C). After the exposing, this was developed using adeveloping solution (trade name: PMER Dev P-7G, manufactured by TokyoOhka Kogyo Co., Ltd.) so that the dissolvable portion of the positivetype photoresist film 24 on the convex portions corresponding to exposedportions was removed, thereby baring the Al thin film 23 on the convexportions (FIG. 6D).

Over the entire surface of the substrate 1 on which this pattern wasformed, an impurity containing amorphous silicon thin film 29 wasfurther formed with a thickness of 30 nm by sputtering method using asilicon target doped with P-type impurities (FIG. 6E). Thereafter, thiswas exposed to ultraviolet rays 30 from the front surface of thesubstrate 1 (FIG. 6F) so that residual positive type photoresist film 24within the concave portion was made dissolvable, and removed by using adeveloping solution (trade name: PMER Dev P-7G, manufactured by TokyoOhka Kogyo Co., Ltd.) (FIG. 6G).

Thereafter, the bared Al thin film 23 was subjected to an etching byusing a mixed acid (mixture of nitric acid and phosphoric acid). At thistime, since the impurity containing amorphous silicon film 29 acts as aresist film, the Al thin film 23 on the convex portions remained as asource electrode 33 and a drain electrode 34, with only the Al thin film23 on the concave portion being removed (FIG. 6H).

Next, a sputtering was carried out over the entire surface of thepatterned substrate 1 by using a silicon target containing no impuritiesso that an amorphous silicon thin film 31 containing no impurities wasformed with a thickness of 50 nm (FIG. 6I).

Thereafter, a laser annealing process was carried out by using a XeClexcimer laser 32 having a predetermined power (FIG. 6J) to crystallizethe amorphous silicon so form a polysilicon thin film to be asemiconductor channel layer 37 (FIG. 6K). Here, with respect to theimpurity containing amorphous silicon thin film 29 and the amorphoussilicon thin film 31 containing no impurities on the Al electrodes, uponcrystallization, the impurities in the impurity containing amorphoussilicon thin film 29 are diffused in the amorphous silicon thin film 31containing no impurities, and these two films are further crystallized.For this reason, these laminated silicon thin film portions were formedas the low resistance source side diffusion layer 38 and the drain sidediffusion layer 39. Moreover, the impurities were activatedsimultaneously due to heat upon crystallization.

Thereafter, a SiO₂ thin film was formed on a polysilicon thin film witha thickness of 100 nm by reactive sputtering method so that a gateinsulating film 36 was formed. Further, an Al film having a thickness of500 nm was patterned on the semiconductor channel layer 37 to form agate electrode 35 so that a thin-film transistor (TFT) of the presentinvention was manufactured (FIG. 6L).

Second Embodiment

After forming a Cr thin film layer having a thickness of 500 nm on aquartz substrate, a pattern of source electrodes and drain electrodeshaving a channel length of 50 μm with a channel width of 50 μm wasformed thereon by a photo-etching method so that a concavoconvex surfaceforming substrate 21 was manufactured. (FIG. 7A).

Between the pattern 22 of this concavoconvex surface forming substrate21 and a substrates formed of non-alkali glass (1737, manufactured byCorning, Inc) having a thickness of 0.7 mm, an uncured transparent UVcuring resin composition was sandwiched and laminated, and this wasexposed to UV-rays from the substrate 1 side so that the UV curing resincomposition was cured. Thereafter, the concavoconvex surface formingsubstrate 21 was demolded so that a concavoconvex surface 2 havingconvex structure having a line width of 50 μm and a height of 500 nm,with a gap of two lines of 50 m, was formed on the substrate 1(FIG. 7A).

An impurity containing amorphous silicon thin film 29 was formed on theresulting concavoconvex surface 2 with a thickness of 30 nm bysputtering method using a silicon target doped with impurities. Next, anegative type photoresist (trade name: THMR-iP, manufactured by TokyoOhka Kogyo Co., Ltd.) was coated thereto by using a spinner to form anegative type photoresist film 24′ having a thickness of 2 μm with aflattened upper surface (FIG. 7B).

The previously used concavoconvex surface forming substrate 21 wasaligned on the negative type photoresist film 24′ at the same positionof the glass substrate as the concavoconvex surface 2 was formed, andmade closely contacted therewith so that the side of the pattern is madecontacted with the negative type photo resist film 24′, and this wasexposed to ultraviolet rays 27 from the concavoconvex surface formingsubstrate 21 side (FIG. 7C). After the exposing, this was developed byusing a developing solution so that the negative type photoresist film24′ was removed except for the film 24′ located on the convex portionscorresponding to the exposed portions; thus, the impurity containingamorphous silicon thin film 29 was bared on the concave portion (FIG.7D).

Thereafter, the bared impurity containing amorphous silicon film 29within the concave portion was etched by using a dry etching device sothat the impurity containing amorphous silicon film 29 within theconcave portion was removed (FIG. 7E). Then, the resist film 24′ wasseparated so that the impurity containing amorphous silicon film 29 wasformed only on the convex portions (FIG. 7F).

Over the entire surface of the patterned substrate 1, an amorphoussilicon thin film 31 containing no impurities was formed with athickness of 50 nm by sputtering method using a silicon targetcontaining no impurities (FIG. 7G). Thereafter, a laser annealingprocess was carried out by using a XeCl excimer laser 32 having apredetermined power (FIG. 7H) to crystallize the amorphous silicon sothat a polysilicon thin film 37 was formed (FIG. 7I). Here, uponcrystallization, the impurities in the impurity containing amorphoussilicon thin film 29 were diffused in the amorphous silicon thin film 31containing no impurities that was laminated on the impurity containingamorphous silicon thin film 29, and further crystallized to form lowresistance source side diffusion layer 38 and drain side diffusion layer39. Moreover, the impurities were activated simultaneously due to heatupon crystallization.

Then, a SiO₂ thin film was formed on a polysilicon thin film with athickness of 100 nm by using a reactive sputtering method so that a gateinsulating film 36 was formed.

Further, contact holes 10 were formed in the gate insulating film 36 onthe source side diffusion layer 38 and the drain side diffusion layer 39by using a dry etching process and the like (FIG. 7J).

Thereafter, an aluminum (Al) film of 500 nm was vapor-deposited on theentire surface, and patterned so that a source electrode 33, a drainelectrode 34 and a gate electrode 35 were formed; thus, a thin-filmtransistor (TFT) was manufactured (FIG. 7K).

Third Embodiment

A concave-shaped pattern having steps with a height of 1.5 μm was formedon a silicon wafer substrate by dry etching method; thus, this wasprepared as a concavoconvex surface forming substrate 21 (FIG. 8A).

Between the pattern side of this concavoconvex surface forming substrate21 and a substrate 1 formed of non-alkali glass (1737, manufactured byCorning, Inc) having a thickness of 0.7 mm, an uncured transparent UVcuring resin composition was sandwiched and laminated, and this wasexposed to UV-rays from the substrate 1 side so that the UV curing resincomposition was cured. Thereafter, the concavoconvex surface formingsubstrate 21 was demolded so that a concavoconvex surface 2 having aconvex-shaped structure having a height of 1.5 μm was formed on thesubstrate 1 (FIG. 8A).

After forming an Al thin film 23 having a thickness of 100 nm over theentire surface of the resulting concavoconvex surface 2 by using asputtering method, an impurity containing amorphous silicon thin film 29was formed over the entire surface of the Al thin film 23 with athickness of 30 nm by sputtering method using a silicon target dopedwith impurities.

Next, a positive type photoresist (trade name: “OFPR800”, manufacturedby Tokyo Ohka Kogyo Co., Ltd.) was coated thereto by using a spinner sothat a positive type photoresist film 24 having a thickness of 2 μm witha flattened upper surface was formed (FIG. 8B).

On this positive type photoresist film 24, a photomask 40 having anopening portion 41, with a size similar to the film thickness of the Althin film 23 and the impurity containing amorphous silicon film 29formed on the step portion, was aligned to the step portion, and madeclosely contacted therewith, and this was exposed to ultraviolet rays 27from the photomask 40 side (FIG. 8C). After the exposing, this wasdeveloped by using a developing solution so that the positive typephotoresist film 24 on the step portion corresponding to the exposedportion was removed; thus, the impurity containing amorphous siliconthin film 29 on the step portion was bared (FIG. 8D).

Thereafter, an etching process of the impurity containing amorphoussilicon film 29 and the Al thin film 23 on the step portion was carriedout by combination of a dry etching device and a wet etching device sothat the impurity containing amorphous silicon film 29 and the Al thinfilm 23 on the step portion were removed (FIG. 8E). Thereafter, byseparating the resist film 24, the impurity containing amorphous siliconfilm 29 and the Al thin film 23 on the concave portion and the convexportion were separated (FIG. 8F).

Over the entire surface of the patterned substrate 1, an amorphoussilicon thin film 31 containing no impurities was formed with athickness of 50 nm by sputtering method using a silicon targetcontaining no impurities (FIG. 8G). Thereafter, a laser annealingprocess was carried out by using a XeCl excimer laser 32 having apredetermined power (FIG. 8H) to crystallize the amorphous silicon thinfilm 31 so that a polysilicon thin film 37 was formed (FIG. 8I). Here,upon crystallization, the impurities in the impurity containingamorphous silicon thin film 29 were diffused in the amorphous siliconthin film 31 containing no impurities that was laminated on the impuritycontaining amorphous silicon thin film 29, and further crystallized toform low resistance source side diffusion layer 38 and drain sidediffusion layer 39. Moreover, the impurities were activatedsimultaneously due to heat upon crystallization.

Thereafter, a SiO₂ thin film was formed on a polysilicon thin film witha thickness of 100 nm by using a reactive sputtering method so that agate insulating film 36 was formed. Further, an aluminum (Al) filmhaving a thickness of 500 nm was deposited on the step portion andpatterned to form a gate electrode 35 so that a thin-film transistor(TFT) of the present invention was manufactured (FIG. 8J).

Fourth Embodiment

After forming a Cr thin film layer having a thickness of 500 nm on aquartz substrate, a concavoconvex surface forming substrate 21 having aconcave portion corresponding to a channel length of 10 μm, and achannel width of 50 μm was prepared by using a photo-etching method(FIG. 9A).

Between the pattern 22 side of this concavoconvex surface formingsubstrate 21 and a substrate 1 formed of non-alkali glass (1737,manufactured by Corning, Inc) having a thickness of 0.7 mm, an uncuredtransparent ultraviolet-ray curing resin composition was sandwiched andlaminated, and this was exposed to ultraviolet rays from the substrate 1side so that the ultraviolet-ray curing resin composition was cured.Thereafter, the concavoconvex surface forming substrate 21 was demoldedso that a concavoconvex surface 2 having a convex-shaped structure witha line width of 10 μm, a length of 50 μm and a height of 500 nm wasformed on the substrate 1 (FIG. 9A).

An Al thin film 23 having a thickness of 100 nm was formed over theentire surface of the resulting concavoconvex surface 2 by using asputtering method. Then, an impurity containing amorphous silicon thinfilm 29 having a thickness of 30 nm was formed over the entire surfaceof the Al surface by sputtering method using a silicon target doped withimpurities. Thereafter, a positive type photoresist (trade name: PMERP-LA900, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was coated theretoby using a spinner, and after the coating, this was heated at 80° C. for30 minutes to form a positive type photoresist film 24 having athickness of 8 μm with a flattened upper surface (FIG. 9B).

The previously used concavoconvex surface forming substrate 21 wasaligned on the positive type photoresist film 24 at the same position asthe glass substrate at the time of forming the concavoconvex pattern,and made closely contacted therewith so that the side of the pattern 22was made in contact with the positive type photoresist film 24, and thiswas exposed to ultraviolet rays 27 from the concavoconvex surfaceforming substrate 21 side (FIG. 9C).

After the exposing, this was developed by using a developing solution(trade name: PMER Dev P-7G, manufactured by Tokyo Ohka Kogyo Co., Ltd.)so that the dissolvable portion of the positive type photoresist film 24on the convex portions corresponding to exposed portions was removed,thereby baring the impurity containing amorphous silicon film 29 to theconvex portions (FIG. 9D).

Thereafter, an etching of the impurity containing amorphous silicon film29 and the Al thin film 23 under the impurity containing amorphoussilicon film 29 was carried out by using a combination of a dry etchingdevice and a wet etching device so that the impurity containingamorphous silicon film 29 and the Al thin film 23 on the convex portionswere removed (FIG. 9E). Thereafter, the resist film 24 was separated(FIG. 9F).

Over the entire surface of the patterned substrate 1, an amorphoussilicon thin film 31 containing no impurities was formed with athickness of 50 nm by sputtering method using a silicon targetcontaining no impurities (FIG. 9G). Thereafter, a laser annealingprocess was carried out by using a XeCl excimer laser 32 having apredetermined power (FIG. 9H) to crystallize the amorphous silicon sothat a polysilicon thin film 37 was formed (FIG. 9I). Here, uponcrystallization, the impurities in the impurity containing amorphoussilicon thin film 29 were diffused in the amorphous silicon thin film 31containing no impurities that was laminated on the impurity containingamorphous silicon thin film 29, and further crystallized to form lowresistance source side diffusion layer 38 and drain side diffusion layer39. Moreover, the impurities were activated simultaneously due to heatupon crystallization.

Thereafter, a SiO₂ thin film was formed on a polysilicon thin film witha thickness of 100 nm by using a reactive sputtering method so that agate insulating film 36 was formed. Further, an aluminum (Al) filmhaving a thickness of 500 nm was deposited on the entire surface andpatterned to form a gate electrode 35 so that a thin-film transistor(TFT) was manufactured (FIG. 9J).

Fifth Embodiment

After forming a Cr thin film layer having a thickness of 500 nm on aquartz substrate, a concavoconvex surface forming substrate 21, having aconcave portion corresponding to a channel length of 10 μm, and achannel width of 50 μm, was prepared by using a photo-etching method(FIG. 10A).

Between the pattern 22 side of this concavoconvex surface formingsubstrate 21 and a substrate 1 formed of non-alkali glass (1737,manufactured by Corning, Inc) having a thickness of 0.7 mm, an uncuredtransparent ultraviolet ray curing resin composition was sandwiched andlaminated, and this was exposed to ultraviolet rays from the substrate 1side so that the ultraviolet ray curing resin composition was cured.Thereafter, the concavoconvex surface forming substrate 21 was separatedso that a concavoconvex surface 2 having a convex-shaped structure witha line width of 10 μm, a length of 50 μm and a height of 1.5 μm wasformed on the substrate 1 (FIG. 10A).

An Al thin film 23 having a thickness of 100 nm was formed over theentire surface of the resulting concavoconvex surface 2 by using asputtering method. Thereafter, a negative type photoresist (trade name:“THMR-iP”, manufactured by Tokyo Ohka Kogyo Co., Ltd.) was coatedthereto by using a spinner to form a negative type photoresist film 24′having a thickness of 2 μm with a flattened upper surface (FIG. 10B).

The previously used concavoconvex surface forming substrate 21 wasaligned on the negative type photoresist film 24′ at the same positionas the position on the glass substrate at the time of forming theconcavoconvex pattern, and made closely contacted therewith so that theside of the pattern 22 was made in contact with the negative typephotoresist film 24′, and this was exposed to ultraviolet rays 27 fromthe concavoconvex surface forming substrate 21 side (FIG. 10C).

After the exposing, this was developed by using a developing solution sothat the negative type photoresist film 24′ was removed except the film24′ located on the convex portions corresponding to the exposedportions; thus, the Al thin film 23 was bared on the concave portion.Then, the Al thin film 23 was subjected to an etching by using a mixedacid (mixture of nitric acid and phosphoric acid) so that the Al thinfilm 23 on the convex portions was allowed to be remained as a gateelectrode 35, with only the Al thin film 23 on the concave portion beingremoved (FIG. 10D). Thereafter, the resist film 24′ was separated (FIG.10E).

Thereafter, a SiO₂ thin film was formed with a thickness of 100 nm byusing a reactive sputtering method so that a gate insulating film 36 wasformed (FIG. 10F).

Over the entire surface of the substrate 1, an amorphous silicon thinfilm 31 containing no impurities was formed with a thickness of 50 nm bysputtering method using a silicon target containing no impurities. Next,by using a silicon target doped with impurities, an impurity containingamorphous silicon thin film 29 with a thickness of 30 nm was formed onthe amorphous silicon thin film 31 containing no impurities (FIG. 10G).

Next, a positive type photoresist (trade name: “OFPR800”, manufacturedby Tokyo Ohka Kogyo Co., Ltd.) was coated thereto by using a spinner toform a positive type photoresist film 24 having a thickness of 2 μm witha flattened upper surface.

The previously used concavoconvex surface forming substrate 21 wasaligned on the positive type photoresist film 24 at the same position asthe position on the glass substrate at the time of forming theconcavoconvex surface 2, and made closely contacted therewith so thatthe side of the pattern 22 was made in contact with the positive typephotoresist film 24, and this was exposed to ultraviolet rays 27 fromthe concavoconvex surface forming substrate 21 side (FIG. 10H). Afterthe exposing, this was developed by using a developing solution so thatthe positive type photoresist film 24 located on the convex portionscorresponding to the exposed portions was removed; thus, the impuritycontaining amorphous silicon thin film 29 was bared.

The impurity containing amorphous silicon 29 was etched by a dry etchingdevice so that the impurity containing amorphous silicon thin film 29 onthe convex portions was removed and the amorphous silicon thin film 31that had not been doped was bared (FIG. 10I).

Thereafter, a laser annealing process was carried out by using a XeClexcimer laser 32 having a predetermined power (FIG. 10J) to crystallizethe amorphous silicon so that a polysilicon thin film 37 was formed(FIG. 10K). Here, with respect to the impurity containing amorphoussilicon thin film 29 and the amorphous silicon thin film 31 containingno impurities, upon crystallization, the impurities in the impuritycontaining amorphous silicon thin film 29 were diffused in the amorphoussilicon thin film 31 containing no impurities, and these two films arefurther crystallized. These laminated silicon thin film portions wereformed as the low resistance source side diffusion layer 38 and thedrain side diffusion layer 39. Moreover, the impurities were activatedsimultaneously due to heat upon crystallization.

Thereafter, an aluminum (Al) film having a thickness of 500 nm wasdeposited and patterned on the thin films of the source side diffusionlayer 38 and the drain side diffusion layer 39 to form a sourceelectrode 33 and a drain electrode 34, thereby providing a thin-filmtransistor (TFT) (FIG. 10K).

The present invention is not limited to the above mentioned embodiments.The above embodiments are merely examples, and whatever havingpractically the same composition and exerting similar functional effectto the technical ideas described in the claims of the present inventionare included in the technical scope of the present invention.

1. A method for manufacturing a thin-film transistor formed by forming asource electrode and a drain electrode on adjacent convex portions of aconcavoconvex surface of a substrate with a concavoconvex surface, andlaminating a gate electrode, a gate insulating film and a semiconductorchannel layer in this order on a bottom surface of a concave areabetween the convex portions, comprising: (1) preparing a substrate and aconcavoconvex surface forming substrate on which a concavoconvex patternis formed; (2) after sandwiching a curing resin composition by the twosubstrates, curing the composition and demolding the concavoconvexsurface forming substrate to form a substrate with a concavoconvexsurface; (3) after forming a conductive thin film over the entiresurface of the concavoconvex surface, further forming a positive typeresist film thereon so that the concavoconvex surface is flattened; (4)exposing and developing the resist film by using a mask having the sameconcavoconvex pattern as the concavoconvex surface forming substrate, tobare the conductive thin film on the top surfaces of the convexportions; (5) forming an impurity containing amorphous silicon thin filmover the entire surface that has been bared; (6) removing the resistfilm and the impurity containing amorphous silicon thin film remainingin the concave areas by exposing and developing from the front side ofthe substrate; (7) etching the bared conductive thin film; (8) formingan amorphous silicon thin film over the entire surface of the substrateafter the etching; (9) carrying out a laser annealing process to form asemiconductor channel layer formed of polysilicon, as well ascrystallizing the impurity containing amorphous silicon thin film on thetop surfaces of the convex portion to form a source side diffusion layerand a drain side diffusion layer formed of low resistance polysilicon;(10) forming a gate insulating film on the semiconductor channel layer,the source side diffusion layer and the drain side diffusion layer; and(11) forming a gate electrode on the gate insulating film of the upperportion of the semiconductor channel layer.
 2. A method formanufacturing a thin-film transistor formed by forming a sourceelectrode and a drain electrode on adjacent convex portion of aconcavoconvex surface of a substrate with a concavoconvex surface, andlaminating a semiconductor channel layer, a gate insulating film and agate electrode in this order on a bottom surface of a concave areabetween the convex portions, comprising: (1) preparing a substrate and aconcavoconvex surface forming substrate on which a concavoconvex patternis formed; (2) after sandwiching a curing resin composition by the twosubstrates, curing the composition and demolding the concavoconvexsurface forming substrate to form a substrate with a concavoconvexsurface; (3) after forming an impurity containing amorphous silicon thinfilm over the entire surface of the concavoconvex surface, furtherforming a negative type resist film thereon so that the concavoconvexsurface is flattened; (4) exposing and developing the resist film byusing a mask having the same concavoconvex pattern as the concavoconvexsurface forming substrate, to bare the impurity containing amorphoussilicon thin film on the concave area; (5) etching the bared impuritycontaining amorphous silicon thin film; (6) removing the resist filmremaining on the top surfaces of the convex portions; (7) forming anamorphous silicon thin film on a predetermined area; (8) carrying out alaser annealing process to form a semiconductor channel layer formed ofpolysilicon on the concave area, as well as crystallizing the impuritycontaining amorphous silicon thin film on the top surfaces of the convexportions on both sides of the concave portion to form a source sidediffusion layer and a drain side diffusion layer formed of lowresistance polysilicon; (9) forming a gate insulating film over theentire surface; and (10) after forming a contact hole in the gateinsulating film, forming a conductive thin film to form a sourceelectrode, a gate electrode and a drain electrode.
 3. A method formanufacturing a thin-film transistor formed by forming either one of asource electrode or a drain electrode on a top surface of a convexportions of a concavoconvex surface of a substrate with a concavoconvexsurface, forming a semiconductor channel layer and a gate electrode on aside surface area connecting to the top surface of the convex portion,forming the remaining one of the source electrode or the drain electrodeon a bottom surface of a concave portion connecting to the side surfacearea of the convex portion, comprising: (1) preparing a substrate and aconcavoconvex surface forming substrate on which a concavoconvex patternis formed; (2) after sandwiching a curing resin composition by the twosubstrates, curing the composition and demolding the concavoconvexsurface forming substrate to form a substrate with a concavoconvexsurface; (3) after forming a conductive thin film over the entiresurface of the concavoconvex surface, further forming an impuritycontaining amorphous silicon thin film thereon, and further forming apositive type resist film thereon so that the concavoconvex surface isflattened; (4) after positioning a photomask, having an opening portionwhich is a size similar to the film thickness of the conductive thinfilm and the impurity containing amorphous silicon thin film that areformed on the side surface area of a step portion of the concavoconvexsurface, on the side surface area on the positive type photoresist filmto be made in contact therewith, exposing and developing from thephotomask side to remove the resist film on the side surface area; (5)etching to remove the bared impurity containing amorphous silicon thinfilm and the conductive thin film; (6) removing the resist film on theconcavoconvex surface; (7) forming an amorphous silicon thin film on apredetermined area including the side surface area; (8) carrying out alaser annealing process to form a semiconductor channel layer formed ofpolysilicon on the side surface area, as well as crystallizing theimpurity containing amorphous silicon thin film of the top surfaces ofthe convex portions and bottom surface of the concave portion connectingto the side surface area to form a source side diffusion layer and adrain side diffusion layer formed of low resistance polysilicon; (9)forming a gate insulating film on the crystallized polysilicon; and (10)forming a gate electrode on the gate insulating film.
 4. A method formanufacturing a thin-film transistor formed by laminating asemiconductor channel layer, a gate insulating film and a gate electrodein this order on a convex portions of a concavoconvex surface of asubstrate with a concavoconvex surface, and forming a source electrodeand a drain electrode respectively on a bottom surface of both sides ofthe concave area between the convex portions, comprising: (1) preparinga substrate and a concavoconvex surface forming substrate on which aconcavoconvex pattern is formed; (2) after sandwiching a curing resincomposition by the two substrates, curing the composition and demoldingthe concavoconvex surface forming substrate to form a substrate with aconcavoconvex surface; (3) after laminating a conductive thin film andan impurity containing amorphous silicon thin film over the entiresurface of the concavoconvex surface, further forming a positive typeresist film so that the concavoconvex surface is flattened; (4) exposingand developing the resist film by using a mask having the sameconcavoconvex pattern as the concavoconvex surface forming substrate, tobare the impurity containing amorphous silicon thin film on the topsurfaces of the convex portions; (5) removing the impurity containingamorphous silicon thin film and the conductive thin film bared by anetching; (6) removing the resist film on the concavoconvex surface; (7)forming an amorphous silicon thin film on a predetermined area includingthe top surfaces of the convex portions; (8) carrying out a laserannealing process to form a semiconductor channel layer formed ofpolysilicon on the top surfaces of the convex portions, as well ascrystallizing the impurity containing amorphous silicon thin film formedon concave areas on both sides of the top surface of the convex portionto form a source side diffusion layer and a drain side diffusion layerformed of low resistance polysilicon; (9) forming a gate insulating filmon the crystallized polysilicon; and (10) forming a gate electrode onthe gate insulating film.
 5. A method for manufacturing for a thin-filmtransistor formed by laminating a semiconductor channel layer, a gateinsulating film and a gate electrode in this order on a convex portionof a concavoconvex surface of a substrate with a concavoconvex surface,and forming a source electrode and a drain electrode formed respectivelyon bottom surface on both sides of the convex portion, comprising: (1)preparing a substrate and a concavoconvex surface forming substrate onwhich a concavoconvex pattern is formed; (2) after sandwiching a curingresin composition by the two substrates, curing the composition anddemolding the concavoconvex surface forming substrate to form asubstrate with a concavoconvex surface; (3) after laminating aconductive thin film over the entire surface of the concavoconvexsurface, further forming a negative type resist film thereon so that theconcavoconvex surface is flattened; (4) exposing and developing theresist film by using a mask having the same concavoconvex pattern as theconcavoconvex surface forming substrate, to bare the conductive thinfilm on the concave portion; (5) removing the conductive thin film baredby an etching; (6) removing the resist film on the concavoconvexsurface; (7) forming a gate insulating film over the entire surfacethereof; (8) forming an amorphous silicon thin film on the gateinsulating film, and further forming an impurity containing amorphoussilicon thin film on the amorphous silicon thin film; (9) carrying out alaser annealing process to form a semiconductor channel layer formed ofpolysilicon on the top surfaces of the convex portions, as well ascrystallizing the impurity containing amorphous silicon thin film formedon concave areas on both sides of the top surface of the convex portionto form a source side diffusion layer and a drain side diffusion layerformed of low resistance polysilicon; and (10) forming a sourceelectrode on the source side diffusion layer, and forming a drainelectrode on the drain side diffusion layer.